Ask HN: What are the top 8 things startups are using Machine Learning for?

Hi! I am studying ML, and I want to build a portfolio of practical projects so that I could get a job in one of the Silicon Valley startups. Ideally it would be several websites that could demonstrate some of the most useful algorithms.

What are some of the most common practical tasks that startups apply ML to?

What kind of projects would be good to have in my portfolio?